In a wireless communication system, a Base Station (BS) allocates UpLink (UL) resources for receiving channel information of a Mobile Station (MS) for the purpose of DownLink (DL) resource allocation. At this time, the kind and period of channel measurement information to have to be reported to UL are determined according to MS's channel state and variation, etc.
FIG. 1 is a diagram illustrating a scheduling architecture within a BS according to the conventional art.
Referring to FIG. 1, an UpLink (UL) scheduler 100 and a DownLink (DL) scheduler 110 operate within the BS.
The UL scheduler 100 allocates UL resources according to a DL channel state reported by each MS. Also, the UL scheduler 100 may change a feedback type, an allocation interval or period, etc. according to a DL channel state of an MS.
The DL scheduler 110 selects a user MS using channel state information from each of MSs and allocates DL resources to the selected MS. The DL scheduler 110 receives a queue size, a waiting time, Quality of Service (QoS) class information from a DL traffic queue 120 and selects the user MS according to predefined scheduling algorithm. The data traffics 120 each queues according to a service type.
A BS determines diversity and band Adaptive Modulation and Coding (AMC) modes and a Modulation and Coding Scheme (MCS) level using feedback information of an MS, and informs the MS of the result. Meantime, the MS can transmit a codebook index together so as to obtain a Multi Input Multi Output (IMO) transmission gain, and the BS may determine an MCS level using this information. For example, the DL scheduler 110 receives channel information from MSs 101 to 104 and then selects user MSs 101 and 104 by predefined scheduling algorithm. The user MS 101 operates in the diversity transmission mode, and the user MS 104 operates in the band AMC transmission mode.
However, a scheme of determining a UL feedback type and period based on an MS's channel state acts as an overhead according to the frequency of generation of DL traffic allocated to an MS. But, although resource allocation timing of the BS for the MS is most affected by a traffic generation distribution, a feedback of channel state information is implemented by periods.
In addition, if the MS 104 is in a band AMC resource allocation mode, the BS receives a channel feedback for each of at least one or more candidate bands requested by the MS 104, and allocates resources to a specific band among the candidate bands. That is, an MS requesting for band AMC allocation has to transmit a channel state feedback by band and a codebook index at all times at a predetermined period in order to receive traffic.
However, in many cases, in an Internet-based non-real time service, traffic having to be transmitted to DL is generated as a burst, and a requirement for transmission delay time is not strict.
As described above, in actual, DL resource allocation is implemented at traffic generation timing for a user MS. That is, only at an interval for which resources are allocated while the user MS is in service connection, a feedback is needed. However, in the conventional art, an MS feeds back channel state information by periods during connection setup with no consideration of traffic generation timing, thus causing an overhead.